1. Field of the Invention
The present invention relates to a wire for a magnetic head with coating which is bonded to a joint body utilizing a ultrasonic bonding apparatus and more particularly, to a wire of micron order coated with urethane resin which is suited to utilize as a signal transfer wire for a thin layer magnetic head mounted on a magnetic disc apparatus.
2. Description of the Prior Art
A wire coated with urethane resin has been heretofore used as a signal transfer wire for a thin layer magnetic head. The coated wire is bonded to the terminal, which is a joint body of the thin layer magnetic head, by soldering.
In the case of soldering, however, heat greatly generates over a wide range of the thin layer magnetic head with an adverse affect. As a result, there is a problem that defective thin layer magnetic heads might be provided.
For this reason, for example, thermocompression bonding system, ultrasonic system, thermocompression bonding system associated with ultrasonic system and the like are proposed, instead of soldering coated wires.
The thermocompression bonding system comprises removing the coated layer on a wire by heating and melting the wire with a bonder of thermocompression bonding apparatus and bonding the wire exposed with the bonder to a joint body.
The ultrasonic system generally comprises previously removing a coated layer on a wire and giving ultrasonic vibration to the wire by a welding chip of ultrasonic bonding apparatus thereby to bond the wire to a joint body. As is shown in Japanese Patent Application KOKAI (Laid Open) (the term "KOKAI" as used herein refers to a published unexamined application) Nos. 42287/1977 and 104787/1977, the ultrasonic system may also be modified by two stage changeover of ultrasonic vibration so that removal of the coated layer and wire bonding can be performed by ultrasonic vibration alone.
The thermocompression bonding system associated with ultrasonic system comprises, as is shown in Japanese Patent Application Kokai No. 59 680/1982, heating the coated layer on a wire with a welding chip to melt as in the thermocompression bonding system and bonding the exposed wire to a joint body through the welding chip by ultrasonic vibration.
These three systems described above may be considered to be preferable because heat acts on a thin layer magnetic head only at an extremely limited area. However, particularly in the thermocompression bonding system and the thermocompression bonding system associated with ultrasonic system, the coated layer on a wire is heated and melts at high temperatures so that there is a fear that defective thin layer magnetic heads might be produced. Accordingly, the ultrasonic system that is free from heating at high temperatures is most suited for bonding a wire as a signal transfer wire for thin layer magnetic head.
In the ultrasonic system as shown in Japanese Patent Application KOKAI Nos. 42287/1977 and 104787/1977, removal of the coated layer on a wire and bonding of the wire can be performed only by ultrasonic vibration; however, a large ultrasonic energy is required for removal of the coated layer in commercially available coated wire in which the coated layer comprises urethane resin and, a primary coat of the terminal as a joint body is thus destroyed by the large ultrasonic energy, reliance is poor and it takes a long time for removal of the coated layer. As a result, too long period of time is required until bonding is completed, which is a problem in operability in a large scale production system.